Diode Laser Safety Calculator
NOHD and eyewear OD for a diode laser beam with different slow- and fast-axis divergence (1/e² or FWHM), on the ICNIRP 2013 eye limits.
Educational only — not compliance-grade
These pages implement the published exposure limits for the cases each one states, but they are educational tools: no laser safety officer has signed them off.
- Do not use these results alone for PPE selection, NHZ / NOHD approval, controlled-area sign-off, enclosure/interlock approval, or formal classification.
- Always verify against ANSI Z136.1, IEC 60825-1, your local procedures, and the responsible laser safety officer / CLSO.
Diode data sheets usually quote FWHM, 1.7× narrower than the 1/e² angle.
ICNIRP 2013, p. 285: 0.25 s (the blink reflex) for an unintended view of a visible beam, 10 s at 700–1400 nm.
NOHD
16.0 m
Governing limit
Retina, thermal
Beam size at the NOHD, slow × fast (1/e²)
16.1 × 48.1 cm
Optical density needed at the aperture
OD 2.90
Set by: Retina, thermal
Peak irradiance at the aperture
127 W/cm²
| Limit | Aperture (mm) | H at t (J/m²) | Hazard distance |
|---|---|---|---|
| Retina, thermal | 7.00 | 164 | 16.0 m |
| Anterior eye (skin limit, 2 × in the IR) | 3.50 | 65775 | 72.0 cm |
An elliptical beam counts as the round beam with the same peak irradiance, of diameter √(dslow dfast), each axis growing as a + rφ (ANSI Z136.1, IEC TR 60825-14). The limits are ICNIRP 2013 (Health Phys. 105:271) at any wavelength, for one exposure of up to t, averaged over each limit's aperture. A bare bar or stack seen up close is an extended source whose larger retinal image raises the limit; that is not modelled, so these are the conservative point-source values. Collimating optics change a and φ: enter the values after them.
Exposure over limit for each eye limit against distance from the emitter. The beam is within the limits where every line is below the dashed line; the marker is the NOHD.
Model and references
Textbook approximation. A standard approximation from the literature (for example paraxial, plane-wave or Gaussian-beam), valid within the range the page states. About the tiers
Elliptical beam as the round beam of equal peak irradiance (√(d_x d_y)), each axis a + rφ; ICNIRP 2013 point-source eye limits averaged over each aperture (its peak if under 1 mm (1/e) on the cornea below 0.35 s, ICNIRP Table 5 note c), one exposure up to t. Not modelled: extended-source bars, pulses.
- ICNIRP (2013). Guidelines on limits of exposure to laser radiation of wavelengths between 180 nm and 1,000 µm. Health Phys. 105(3), 271–295. Tables 5 and 8. doi:10.1097/HP.0b013e3182983fd4
- ANSI Z136.1-2014, American National Standard for Safe Use of Lasers. Appendix B: nominal hazard zone, NOHD and optical density.
- IEC TR 60825-14:2004, Safety of laser products – Part 14: A user's guide. Hazard distances and protective eyewear.